Browsing by Author "Yang, Ming"
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Item Adherence to treatment guidelines and survival for older patients with stage II or III colon cancer in Texas from 2001 through 2011(Wiley, 2018) Zhao, Hui; Zhang, Ning; Ho, Vivian; Ding, Minming; He, Weiguo; Niu, Jiangong; Yang, Ming; Du, Xianglin; Zorzi, Daria; Chavez-MacGregor, Mariana; Giordano, Sharon H.BACKGROUND: Treatment guidelines for colon cancer recommend colectomy with lymphadenectomy of at least 12 lymph nodes for patients with stage I to stage III disease as surgery adherence (SA) and adjuvant chemotherapy for individuals with stage III disease. Herein, the authors evaluated adherence to these guidelines among older patients in Texas with colon cancer and the associated survival outcomes. METHODS: Using Texas Cancer Registry data linked with Medicare data, the authors included patients with AJCC stage II and III colon cancer who were aged ?66 years and diagnosed between 2001 and 2011. SA and adjuvant chemotherapy adherence rates to treatment guidelines were estimated. The chi-square test, general linear regression, survival probability, and Cox regression were used to identify factors associated with adherence and survival. RESULTS: The rate of SA increased from 47.2% to 84% among 6029 patients with stage II or stage III disease from 2001 to 2011, and the rate of adjuvant chemotherapy increased from 48.9% to 53.1% for patients with stage III disease during the same time period. SA was associated with marital status, tumor size, surgeon specialty, and year of diagnosis. Patient age, sex, marital status, Medicare state buy-in status, comorbidity status, and year of diagnosis were found to be associated with adjuvant chemotherapy. The 5-year survival probability for patients receiving guideline-concordant treatment was the highest at 87% for patients with stage II disease and was 73% for those with stage III disease. After adjusting for demographic and tumor characteristics, improved cancer cause-specific survival was associated with the receipt of stage-specific, guideline-concordant treatment for patients with stage II or stage III disease. CONCLUSIONS: The adherence to guideline-concordant treatment among older patients with colon cancer residing in Texas improved over time, and was associated with better survival outcomes. Future studies should be focused on identifying interventions to improve guideline-concordant treatment adherence.Item Impact of dose calculation accuracy on inverse linear energy transfer optimization for intensity-modulated proton therapy(Wiley, 2023) Chen, Mei; Cao, Wenhua; Yepes, Pablo; Guan, Fada; Poenisch, Falk; Xu, Cheng; Chen, Jiayi; Li, Yupeng; Vazquez, Ivan; Yang, Ming; Zhu, X. Ronald; Zhang, XiaodongObjective To determine the effect of dose calculation accuracy on inverse linear energy transfer (LET) optimization for intensity-modulated proton therapy, and to determine whether adding more beams would improve the plan robustness to different dose calculation engines. Methods Two sets of intensity-modulated proton therapy plans using two, four, six, and nine beams were created for 10 prostate cancer patients: one set was optimized with dose constraints (DoseOpt) using the pencil beam (PB) algorithm, and the other set was optimized with additional LET constraints (LETOpt) using the Monte Carlo (MC) algorithm. Dose distributions of DoseOpt plans were then recalculated using the MC algorithm, and the LETOpt plans were recalculated using the PB algorithm. Dosimetric indices of targets and critical organs were compared between the PB and MC algorithms for both sets of plans. Results For DoseOpt plans, dose differences between the PB and MC algorithms were minimal. However, the maximum dose differences in LETOpt plans were 11.11% and 15.85% in the dose covering 98% and 2% (D2) of the clinical target volume, respectively. Furthermore, the dose to 1 cc of the bladder differed by 11.42 Gy (relative biological effectiveness). Adding more beams reduced the discrepancy in target coverage, but the errors in D2 of the structure were increased with the number of beams. Conclusion High modulation of LET requires high dose calculation accuracy during the optimization and final dose calculation in the inverse treatment planning for intensity-modulated proton therapy, and adding more beams did not improve the plan robustness to different dose calculation algorithms.Item Optimization of FLASH proton beams using a track-repeating algorithm(Wiley, 2022) Wang, Qianxia; Titt, Uwe; Mohan, Radhe; Guan, Fada; Zhao, Yao; Yang, Ming; Yepes, PabloBackground: Radiation with high dose rate (FLASH) has shown to reduce toxicities to normal tissues around the target and maintain tumor control with the same amount of dose compared to conventional radiation. This phenomenon has been widely studied in electron therapy, which is often used for shallow tumor treatment. Proton therapy is considered a more suitable treatment modality for deep-seated tumors. The feasibility of FLASH proton therapy has recently been demonstrated by a series of pre- and clinical trials. One of the challenges is to efficiently generate wide enough dose distributions in both lateral and longitudinal directions to cover the entire tumor volume. The goal of this paper is to introduce a set of automatic FLASH proton beam optimization algorithms developed recently. Purpose: To develop a fast and efficient optimizer for the design of a passive scattering proton FLASH radiotherapy delivery at The University of Texas MD Anderson Proton Therapy Center, based on the fast dose calculator (FDC). Methods: A track-repeating algorithm, FDC, was validated versus Geant4 simulations and applied to calculate dose distributions in various beamline setups. The design of the components was optimized to deliver homogeneous fields with well-defined diameters between 11.0 and 20.5 mm, as well as a spread-out Bragg peak (SOBP) with modulations between 8.5 and 39.0 mm. A ridge filter, a high-Z material scatterer, and a collimator with range compensator were inserted in the beam path, and their shapes and sizes were optimized to spread out the Bragg peak, widen the beam, and reduce the penumbra. The optimizer was developed and tested using two proton energies (87.0 and 159.5 MeV) in a variety of beamline arrangements. Dose rates of the optimized beams were estimated by scaling their doses to those of unmodified beams. Results: The optimized 87.0-MeV beams, with a distance from the beam pipe window to the phantom surface (window-to-surface distance [WSD]) of 550 mm, produced an 8.5-mm-wide SOBP (proximal 90% to distal 90% of the maximum dose); 14.5, 12.0, and 11.0-mm lateral widths at the 50%, 80%, and 90% dose location, respectively; and a 2.5-mm penumbra from 80% to 20% in the lateral profile. The 159.5-MeV beam had an SOBP of 39.0 mm and lateral widths of 20.5, 15.0, and 12.5 mm at 50%, 80%, and 90% dose location, respectively, when the WSD was 550 mm. Wider lateral widths were obtained with increased WSD. The SOBP modulations changed when the ridge filters with different characteristics were inserted. Dose rates on the beam central axis for all optimized beams (other than the 87.0-MeV beam with 2000-mm WSD) were above that needed for the FLASH effect threshold (40 Gy/s) except at the very end of the depth dose profile scaling with a dose rate of 1400 Gy/s at the Bragg peak in the unmodified beams. The optimizer was able to instantly design the individual beamline components for each of the beamline setups, without the need of time intensive iterative simulations. Conclusion: An efficient system, consisting of an optimizer and an FDC have been developed and validated in a variety of beamline setups, comprising two proton energies, several WSDs, and SOBPs. The set of automatic optimization algorithms produces beam shaping element designs efficiently and with excellent quality.